Draft gear for railroad cars



Nov. 3, 1959 W. K. MaCCURDY 2,911,112

DRAFT GEAR FOR RAILROAD CARS Filed Nov. 5, 1954 5 Sheets-Sheet l Nov. 3,1959 w. K. MaCcuRDY l DRAFT GEAR FOR RAILROAD CARS 5 Sheets-Sheet 2Filed Nov. 5, 1954 IN V EN TOR.

W/LL/AM KM CURDY Bmm A TTORNEVS NOV. 3, 1959 W. K. MaCCURDY 2,911,112

DRAFT GEAR FOR RAILROAD CARS INVENTOR. WILL/AM KMMCURDY IWW/ @@Mm A TTORNEKS Nov. 3, 1959 w. K. MaCcuRDY DRAFT GEAR FOR RAILROAD CARS 5Sheets-Sheet 4 Filed Nov. 5. 1954 --q/Ioa JNVENToR. W/LL/AMKM CURDYATTORNEYS Nov. 3, 1959 w. Kt. MaCURDY DRAFT GEAR FOR RAILROAD CARS 5Sheets-Sheet 5 Filed Nov. 5, 1954 INVENTOR. W/LL/AM K M CURDV [im 4(444km A 7' TOR/VEYS 2,911,112 DRAFT-GEAR roR RAILROAD cARs william K.Maccurdy, Menld Park, Ca1if.,assignor, by mesne assignments, to SouthernPacific Company, San

Francisco, Calif., a corporation of Delaware l, f Applicare@ November s,1954, serial No. 467,118

' #13 Claims. (cl. 213-8) This invention relates to and in general hasfor its object the provision of improved draft gear for railroad cars. v

As is well known in the industry, a very substantial loss is sufferedannually by railroads as a result of freightk damaged by the jarring offreight cars during the operation thereof particularly in retarderyards. This loss still occurs in spite of the fact that many attemptshave K been made to devise satisfactory mechanisms for cushioning theimpact to which freight cars aresubjected and to devise systems forcontrolling and limiting the speeds of cars in retarderv yards.

lMorespeciiically one of the objects ofthis inventionY is the provisionof draft gear including a draft sill paralleling vthe main sill of afreight car and longitudinally movable relative thereto under theinfluence of an impact to which the car is subjected; a hydraulic pressmounted on one of said sills; two sets of interdigitated friction platesoperatively disposed in said press, one set being secured to `one silland the other set to the other sill; a hydraulic pump mounted on one ofsaid sills and operatively connected to said hydraulic press; and meansresponsive to the relative movement of said sills for actuating saidhydraulic pump thereby to activate said hydraulic press and squeeze saidfriction plates and .thereto restrain the relative movement of saidsills.

A further object of this invention is the provision in draft gear suchas above described of friction plates movable with the draft sill andwhich are maintained under' tension rather than compression during thedampening action" of vthe draft gear.

Still another object of this invention is the provision of `draft gearof the character described, wherein the hydraulic pump is provided witha metering pin for controlling the pressure developed throughout theworking medium.

The invention possesses other advantageous features, some of which, withthe foregoing, willbeV set forth at length in the following descriptionwhere those forms of the invention which have been selected forillustration in the drawings accompanying and forming a part of thevpresent specification, are outlined in full. In said drawings, severalforms ofthe invention are shown, but it is to be understood that it isnot limited to such forms, since the invention as set forth in theclaims may be embodied in other forms.

Referring to the drawings:

."Figure 1A is a top plan view of the end of a freight car'sub-frarneincluding draftA gear embodying vthe objects of myv inventionand withportions thereof broken away to better illustrate Aits construction. l

' Figure 1B is a continuation of the sub-frame and draft gear disclosedin Figure 1A, its right-hand end terminating at about the longitudinalmidpoint of the sub-frame.

Figure 2A'is a vertical midsection of the structure illustrated inFigure 1A.

Figure 2B is avertical midsectitni of the structure illus-.

fr ICC 2 trated in Figure lB, with portions thereof broken awa to betterillustrate its construction.

Figure 3 is a transverse vertical section taken on the section-line 3-3of Figure 2B. A i

,Figure 4 is a view similar to that illustrated in the right-hand end ofFigure 2B, but somewhat enlarged and showing the piston of the hydraulicpump at the end of its work stroke.

Figure 5 is an enlarged vertical transverse section taken on the sectionline 5-5 of Figure 2B.

Figure 6 is an enlarged transverse vertical section taken on the sectionline 6-6 of Figure 2A.

Figure 7 is a top lplan viewof a modified formof hydraulic pumpactuating element.

Figure 8 is a longitudinal vertical' section of the hydraulic pumpactuating element illustrated in Figure 7.

Figure 9 is a right-hand end elevationof theistructure shown in Figure8. f

Figure 10-is'a top plan view of an alternate friction plate assembly. f

Figure 1l is a vertical midsection of the assembly illustrated in Figurel0. Y

Figure 12 is a right-hand end elevation of Figure 10.

vGeneral Description Briefly the structure disclosed in Figures lA to 6in-V -;clusive comprises a freight car sub-frame including a main sillextending the length thereof. Mounted adjacent the'main sill inparallelism therewith is a draft sill protruding beyond the main sillateach end thereof.

Supported by the main silll intermediate'its lends is a .hydraulic pressand operatively disposed therein are two` interdigitated sets offriction plates, one fastened to the main sill and the other fastened toand movable with the'draft sill.

I Car sub-frame and sill assem'bly" More specifically the structuredisclosed in Figures 1Ai to 6 inclusive comprises a freight car bodycenter sill 11 surrounding a draft sill 12 `and representing the under-Vframe of the car body. Forming a part of said underframe are end sills13, bolsters 14,` crossbearers 15 and cross ties 16, all essentially ofstandard design and modifiedl only to accommodate for the wider spacingof the center sill 11 and to provide proper support and clearg ance forthe sliding draftsill 12. Most radically affected bythese requirementsis the combined center plate and bolster bottom tie 17 shown in thedrawing as a single casting, *but which can be of built-up weldeddesign.

Coupler assembly Associated with each end of the draft sill 12 is astandard coupler 18 provided with a slotted shank 19, a coupler carrier20, coupler yoke 21, coupler key 22, yoke carrier 23,V draft gear 24,'front draft lugs 25 and `rear draftlugs 26. As is well known in the art,this lstructure willabsorb bufng shocks Aof certain magnitudes beforeaffecting the car body center sill 11. How-l Mounted on one of the sillsis a hydraulic' pump operatively associated with the hydraulic press,and'- ing .hydnaulically actuated friction mechanism generally indicatedby the reference numeral 28. Preferably one such assembly and mechanismis installed at each end of the vfreight car. Y

Spring return centering assembly -lugs33 securedto thetop flangesthereof serving as seats or stops for follower plates 30. Similarly andfor a like purpose, lugs 34 .are attached to the center sill bottom tieplates 35. Optionally the springs 29 can be housed in tubes 36, a rod 37r'extending `through the springs 29 and follower plates 30 withppositiveclearance, being used to vfacilitate the installation and removal of thesprings. It *will be seen that as a result of this construction, themovementzof the draft sill 12 relative to the centersill 11 in eitherdirection rwill compress the springs in an amount. proportional to therelative movement between these sills, and that the springs will exertan yequal and opposite reaction on the sills.

Friction plate assembly ably, and as illustrated, the plates 38 and 39are of inverted V-shape to provide forgreater column strength when theplates function under compression but can beY made flat if, as shown inFigures 10, l1 and l2, they are `made to function under tension.

Removably secured to the draft sill 12 and movable therewith are a pairof longitudinally spaced plates 40 reinforced by ribs 41, the slidingfriction plates 38 being accommodated between the plates 40 andtherefore con-A strained to move therewith under the pushing action ofone of the plates 40.= Y

Forming a stationary or fixed retainer for the friction plates 39 aretwo laterally spaced pairs of posts 42, there being one pair of suchposts located on each side 'of the sliding friction plates 38 and eachsuch pair of posts being welded to a longitudinally extending side plate43. Welded between and to the upper ends of the posts 42 is a pressureblock 44 having an inverted V-shaped bottom conforming to the contour ofthe friction plates 38 and 39. Bolted to and across the bottom of thecenter sill 11 (Figure 6) below the plates 38 and 39 is a tie plate 45and 'mounted on the plate 45 is a vertically movable pressure block orsaddle 46 for supporting the two interdigitated sets of friction plates38 and-39, the plates 39 being confined with the retainer formed by the.posts 42 and plates 43. Here it should be noted that the ends of thestationary friction plates 39 abut the posts 42 and are thereforerestrained against longitudinal movement, that the sliding frictionplates 38 pass between the posts 42 with positive clearance but4 areseated between the plates 40 and are therefore constrained to move withthe draft sill 12.

To clear the pressure block 44 the top flanges ofthe draft sill V12 arecut out and the sill reinforced at this point .by angles 47. Formed asan integral part of the center sill 11 is a top tie plate 48, the centerthereof being'cut out for the snug reception vof the top ofthe pressureblock 44. These'expedients Vare resorted to only because the draft gearhere under consideration is being installed on a freight car sub-frameof conventional con-` struction, and not on a sub-frame specificallydesignedto accommodate such draft gear.

Hydraulic pump assembly Associated with the friction mechanism 28 abovevdescribed is a hydraulic pump assembly generally designated by thereference numeral 49 and a hydraulic press generally designated by theVreference numeral 50.

As best shown in Figures 4 and 5, the hydraulic pump 49 comprises amaster cylinder 51 secured to the center sill bottom plate 52, a piston53 operatively disposed within the cylinder 51, a piston rod 54 securedto said piston, across head 55 secured to the free end of said pistonrod, and a mechanical linkage between the cross head and the draft sill12 whereby any movement of the latter relative to the center sill 11will actuate the piston 53. To this end, there is pivoted to the crosshead 55 a pair of opposed channels 56,l these channels 1in turn beingpivoted at their ends to the upper ends of depending links 57. The lowerend of each of the links 57 is pivoted to a bracket 58 bolted orotherwise secured to the draft sill 12. Secured to the sill bottom plate52 are a pair of guide members 59 of I-beam cross-section forconstraining the cross head 55 and channels 56 to move vertically andthereby causing the piston 53 to move withinA the cylinder 51. Anytranslatory motion of the draft sill 12 from its neutral or centerposition as illustrated in Figure 2B, will cause thelinks 57 andchannels 56 to move from their positions as shownin Figure 2B towardtheir positions as shown in Figure 4 and perforce cause the piston totravel downwardly.

From an inspection of Figure 4 it will be noted that the piston 53`isprovided with an `axial bore 60 having a restricted throat 60a andintersected by a transverse bore 60h. Mounted-on the lower end of thecylinder 51 coaxially therewith is a metering pin 61 extending into bore60 and so Vshaped as to control the rate of ow ofworking medium throughthe restricted throat 60EL and thus determine the desired pressure.Connected to the bottom of the cylinder 51 are conduits 62 and 63, theformer communicating with the hydraulic press 50 and the latter to thelower end of a relief Valve 64. Connected with the upper end of thecylinder 51 and with the upper endy Hydraulic press Secured to thecenter sill bottom plate 45 is a closed cylinder 68 and slidablydisposed within said cylinder is a piston 69 supported by anintermediate spring 76. Supported by the cylinder 68 adjacent its sidewalls, is a pair of diametrically opposed springs 71 extending throughthe top of the cylinder and through the plate 45 into engagement withthe pressure block or saddle 46, thereby to subject the friction plates3S and 39 to an initial predetermined pressure.

As best indicated in Figure 6, the conduit 62 communicates with thelower end of the cylinder 68 whereby the conduit 67 is connected to theupper end thereof. kEstablishing communication between the upper andlower ends of the cylinder 68 is a conduit 72, a check valve 73 beinginterposed in this conduit so as to permit only the downward ow ofworking medium therethrough.

Operation out the rest ofthe hydraulic system, all in accordance.

with'well known hydraulic principles. There is essentially no flow ofliquid in the usual sense, except from below to above the piston 53, butrather there is a shock or pressure wave transmitted through the liquidwhich acts directly against the piston 69 'and which in turn must besure'so developed bythe pump assembly istr'ansmitted through the conduit62 to the cylinder 68 of the hydraulic press 50 thereby to activate thepiston 69 and compress the interdigitated sets of friction plates 38 and39. Since one set of plates is fixed to the car main sill11, and sincethe other set moves with the draft sill 12, any movement ofthe draftsill' away from its neutral or` center position will be retarded by thecompression of the two sets of friction plates. Furthermore since thecompression of the friction plates proceeds in response to the relativemovement of the two sills, the draft gear described may be characterizedas being of the servo type. t

Preferably the braking action of the friction plates 38 and 39V shouldbe proportional' to the impact on the draft `sill 12 causing relativemotion between the two sills. Since the movement ofthe draft sill 12 isproportional to such impact, it can be said that the braking of thefriction plates should be proportional to the movement of the draftsill. In the modification of the device above described, the movement ofthe pump piston 53 is not directlyproportional to the movement of thedraft sill 12, but rather a function of tan a, a being the angle betweenthe links 57 and a vertical reference line. To compensate for this, andto make the pressure applied by the hydraulic press 50 to the frictionplates 38 and 39 directly proportional; tothe impact on the draft sill,the metering pin 61 jof the hydraulic pump piston 53 may be shaped asrequied; vThe same `objective could of course be attained 4by anyanalogous method which will vary the flow of the working medium in thesame manner during the stroke. I

' Modified hydraulic pump assembly Y u lIn .Figures 7,v 8 and 9 stillanother alternative for making the braking action of the friction plates38 and 39 directly. proportional to the movement vof the draft sill 12`has 'been illustrated. Here the system is exactly the same as shown inFigures 1A to 6 inclusive, except with respect Vto the mechanism foractivating the hydraulic pump. For purposes of ready reference andcomparison, all parts to which no kchange has been made will be identiedby the corresponding reference numerals 'used in conjunction withFigures 1A to 6 inclusive', whereas new or altered parts will beindicated by a new set of reference numerals beginning with the number100.

Included in the modified hydraulic pump assembly generally designated bythe reference numeral 100 'is the cylinder 51 which asv previouslydescribed is secured to theV center sill bottom plate 52; piston 53,piston rod 54, and a crosshead 101 having oppositely inclined upperfaces 101a and 1010. Mounted on the bottom plate 52 are four guides 102of T-cross section fortconstrainingv the crosshead 101 and the pistonrod 54 to move only vertically. Secured to the draft sill 12 is amounting plate 103 and fastened thereto is a cross-head actuating plate104, provided on its lower side with a pair of opposed and converginginclined planes 104@L and v 104b respectively, complementary to thefaces 101a and 1011. Slidably mounted in the top and bottom plates ofthe fore be easily fashioned tol translate the movement of the piston 53into a force applied by the hydraulic press to'the friction plates 38and 39 such that the braking force effected 'bythe plates 38 rand 39will be directly proportional to any impact to which the draft sillmaybe subjected and which is suflicient to effect any appreciablemovement of the draft sill.

Alternatey construction of friction plat-e lzllssnembly In the frictionplate assemblyY illustratdgin Figures Y 1A', 2A and'6, the movement ofthe draft sill 12 is transmitted to slidable friction plates 38 by thepushing vaction of the trailing plate 40. Aspreviously stated the columnstrength of a relatively thin plate is low and it is for that reasonthat friction plates of V shape section are resorted to in'F-ig'ures 1A,2A yand 6. Although a relativelythin but long plate lacks strength whenyplacedunder longitudinal compression, it nevertheless hasconsiderable'lo'n- 'gitudinal tensional strength. In the modificationillustrated in Figures l0, 1.1 and 12, advantage is taken of thisphenomena by so arranging the friction plate assembly that thetslidingfriction plates 38 are pulled by the draftnsill 12 in response to anymovement of said sill in either' direction. Here again the referencenumerals heretofore used will be applied to identical'parts and newreference numerals beginning with 200, reserved for` new or modifiedparts or elements. More specifically the friction plater assemblydisclosed l in Figures 10, 11 and 12 and generally indicated by thereference numeral 200, include a first set of relatively long and narrowsliding friction plates 201 interdigitated cylinder 51 and in the centersill bottom plate-.'52, are a The-"springs-106 therefore serve tomaintain the crosshead v 1.0' 1 y in positive and sliding engagementwith the inclined planes 104EL and 104i.

it As a result of this construction Ait will be seen that any movementof the draft sill 12 in either direction will serve to depress thecrosshead 101 and its associated pis-,

ton 53, and that the downward movement of thepiston is a straight linefunction of the movement of the draft sfil'l412. 'The'contourofthenmetering p in ,61; can therewith a second yset of relatively shortstationary or fixed friction plates 202. Disposed between the endsofplates 201 in abutment with shoulders -201a formed on the ends offtheplates 201 are follower bars 203. Secured to the draft silll`2'in'wardly of the follower bars 203 and in contact therewith are lugs204. To securely lock the ends of the friction plates 201 to thefollower barsI 203;' filler blocks 205 are snugly fitted between the`uppermost friction plate 201 and the top of the draft 'sill 12 andbetween the lowermost friction plate 201 and the draft sill bottom plate206. As a result of this construction the ends of the slidable frictionplates are interdigitated with and irmlysecured to the followerbars'v203, .the bars 203 being in contact with the lugs 204.` Consequentlydraft sill 12 moves to the left asv viewed in Fig. 1l, and theleft-handvlugs 204 'will serve to, pull the friction` plates 201 to,thev leftover the stationary friction plates 202. When the draft sillmoves to. the right as viewed in Figure 1l, the right-hand lugs 204 willpull the plates 201 to the right. In each case the plates 201operate'under tension rather than under compres-' sion whereby ,allpossibility oftbuckling isobviated. Asin'the cas'eof the friction plateassembly illus-A trated in FiguresflA, 2A .and 6, the stationaryfriction plates 202 are housed by the posts 42 welded to the side plates43 and to an X-shaped block 207 tted between the upper ends of the posts42. The lower ends of the posts 42 are welded to the center sill bottomtie plate 4S which in turn is bolted to the center sill 11.

Disposed beneath the lowermost friction plate 202 and forming a supporttherefor is a block208. The remainder of the assembly is identical tothe assembly originally describedv and therefore the elements thereofbear the same reference numerals.

It is evident that in all modifications of the general Vcombinationherein described a moderate end fimpacton,r

thetdraft sill willl produce a moderate pressure on the friction platesresulting in a moderate retardation vin the relative movement betweenthe draft sill and the centerV sill. Under a larger impact load, thevelocity ofthe draft;

sill will be greater, thereby resulting in a greater velocity of thepiston of the hydraulic pump and the application ofv a greater pressureby the hydraulic press tothe fricv tion plates. l'In' other words thepressure applied'to the 1. Draft gear for a railroad car having astationaryv part and almovable part movable relative to said stationarypart in opposite directions from normal at-rest position, said draftkgear comprising: a hydraulic press having opposed, spaced pressureplates; a stack of first and second sets of interdigitated frictionplates operatively disposed in said press in confronting face to facerelationship With and between said pressure plates -for compressionthereby, the friction plates of one set of plates being arranged forsliding movement over the friction plates of the other `set of plates;one of said sets of friction plates vbeing'connected to said stationarypart of said railroad car and the second of said sets of friction platesconnected to and movable with said relatively movable part of said car,spring means biasing said pressure plates together; a hydraulic pump foractuating said hydraulic press; and means for actuating said hydraulicpump in response to movement of said movable part relative to saidstationary part in a direction away from said normal at-rest position.

2. Draft gear such as defined in claim 1 wherein said hydraulic pumpincludes a cylinder; a piston slidable in said cylinder and formed withan axial bore; and a `tapered metering pin secured to one end of saidcylinder coaxiall-ytherewith and extending into said bore fordetermining the rate of flow of liquid through said bore thusdetermining the pressure applied to said hydraulic press.

V3. Draft gear for railroad cars comprising: a car subframe sill; adraft sill paralleling said sub-frame sill and arrangedA forlongitudinal movement relative thereto; means engaging said sills andbiasing said draft sill against movement relative to said subfrarne sillin a direction away from a normal at-rest position; a rst set offriction plates fixed to said subframe sill;-a second set of frictionplates fixed to said draft sill, the plates of said second set beinginterdigitated with the friction plates of s'aid first set to form astack; a hydraulic press mounted on one of said sills and having opposedpressure plates straddling said interdigitated friction plates andvengaging the outerl faces of the outer plates of the stack; a `hydraulicpump mounted on one of said sills; means for conducting fluidbetween the pump and press for actuating said press by the pump; andmeans responsive to movement of said draft sill in a direction away fromsaid normal at-rest position forV actuating said pump.

4. Draft gear such as defined in claim 3 wherein said hydraulic pumpincludes a cylinder; apiston S'lidable in said cylinder and .formed withVan axial f bore; and a tapered metering pin secured to one end of saidcylinder coaxially therewith and extending into said bore fordetermining the flow of liquid through said bore'thereby to determinethe pressure applied to said hydraulic press.

5. Draft gear for `a railroad car having a stationary part and a movablepart movable relative to said stationaryv part in opposite directionsfrom a normal at-rest position, said draft gear comprising: a hydraulicpress; first and second sets of interdigitated friction plates disposedin confronting Vface to face relationship in said press for theapplication of compressive force thereby to the plates; normal to theirfaces, the-friction plates of one set of :plates being arranged forsliding movement, over'the friction plates of said second setv offriction plates, the plates of the first set being connected to andmovable withV said movable part and the plates of the second set beingconnected to said stationary part; means operatively connected to saidplates and biasing said plates together; and means for actuating said.hydraulic press in response to movement of said movable part of Ythecar relative to said stationary part and in aldirection away from saidnormal at-rest position, thereby to squeeze said plates together. y

l 6. Draft gear fora railroad car having a stationary part anda movablepart movable relative to said stationary part in opposite directionsfrom a normal yat-rest position, said draft gear comprising: a hydraulicpress; first and second sets of interdigitated friction plates disposedin confronting face to face relationship in said press for theapplication of compressive force thereby to the plates normal to theirfaces, the friction plates of one set of plates being arranged forsliding movement over the friction plates of said second set and theplates of the first set being connected to andv movable with saidmovable part and the plates of the second set being connected to saidstationary part; a hydraulic pump .for actuating said hydraulic press,said pump including `a cylinder, a piston slidable'in said cylinder andformed with anA axial bore; a tapered metering pin secured'to one end ofsaid cylinder coaxial -therewith and extending into said bore fordetermining the pressure applied to the hydraulic press; and meansresponsive to movement of said movable part of the carrelative to saidstationary part and in a direction away from said normal alt-restposition for actuatingsaid hydraulic pump,

7. Draft gear for railroad cars comprising: a car subframe sill; a draftsill paralleling said subframe sill and arranged 'for longitudinalmovement relative thereto in opposite directions from a normal art-restposition; a rst set of friction plates fixed to said frame sill; asecond set of friction plates fixed to said draft sill, the plates ofsaid second set being interdigitated in confronting face V'to facerelationship with the friction plates of said first set to form a stack;a hydraulic press mounted on one of said sills and acting on the outerfaces of the outer plates of the stack to compress said plates; ahydraulic pump mounted on one of said sills for actuating said press;means responsive to movement of said draft sill relative to saidsubframe sill and in a direction away from said normal at-rest positionfor actuating said pump, said pump including a'cylinder and a pistonslidablevtherein and formed with an axial bore; and ay tapered meteringpin secured to one end of said cylinder coaxially therewith `andextending into said bore for determining the flow of liquid through saidbore thereby to determine the pressure applied to said hydraulic pressVby the pump,

8. Draft gear for a railroad car having a stationary part and a movablepart movable relative to said stationary part in opposite directionsfrom a normal at-rest position, said draft gear comprising: a hydraulicpress; first and second sets of interdigitated friction platesoperatively disposed in confronting face `to face relationship in saidpress for the application of compressive force thereby to the platesnormal to their faces, the plates Vof one of said sets being connectedto and movable with said relatively movable part of said railroad carand being arranged for sliding movement parallel to the planes of theirfaces over the plates of the other of said sets, the plates of saidother of said setsbeing connected to said stationary part of said car;and means connected to one of said parts responsive to movement of saidmovable part of said car relative to said stationary part and inadirection away from said normal at-rest position for actuating the pressto compress the plates.

9. Draft gear as ydefined in 'claim 8 wherein said last named meansincludes a cylinder, a piston in said cylinder and co-operatingtherewith to define -a pressure chamber, means responsive to saidrelative movement in said direction to move said piston in a directionto reduce the size of said pressure chamber, means providing for fluidiiow from said chamber, and means for variably restricting said iiow tovary the pressure within said chamber during .said piston movement,.said includingmeans for transmitting the uid pressure within saidpressure charn-l l0. Draft gear .as deiined in claim 9 wherein saidmeans for variably restricting said flow comprises means defining anaxial bore in said piston and a tapered metering pin secured to one endof said cylinder coaxial with said bore and movable into said bore forvariably restricting the flow of uid through said bore to vary thepressure within said chamber.

1l. Draft gear as defined in claim 8 wherein said last named means isresponsive to the rate of movement of said movable part relative to saidstationary part in a direction away from said normal at-rest position.

12. Draft lgear as defined in claim 8 wherein said last named means isresponsive to the rate of movement and displacement of said movable partrelative -to said stationary part and in a direction away from saidnormal at-rest postion.

13. In a railway car having an underframe member and a draft sill membermounted on said underframe member for longitudinal movement relativethereto in opposite directions from a normal `at-rest position, thecombination of two sets of friction plates with the plates of one setinterdigitated with those of the other in confronting face to facerelationship to form a stack with the faces of the plates parallel tothe direction of movement of the draft sill member, means connecting theplates of the rst set to said underframe member against longitudinalmovement relative thereto, means connecting the plates of the second setto the draft sill member for movement Itherewith longitudinally of saidunderfrarne member, means responsive to movement of said draft sillmember relative to said underframe member vand in a direction away fromsaid normal at-rest position to apply a'compressive force to said stackof plates normal to the faces thereof, said last named means including acylinder mounted on one of said members, a piston reciprocably mountedwithin said cylinder, means carried by said cylinder and biasing saidpiston in one direction relative to said cylinder, co-operating means onthe other of said members and on said piston and responsive tolongitudinal movement of said draft sill member relative to saidunderframe member and in a direction away from said normal at-restposition to move said piston in the direction opposite to said directionof said first mentioned piston movement to provide -a working pressurewithin said cylinder at `one side of said piston, means for conductingfluid between the parts of the cylinder at opposite sides of the pistonfor controlling said working pressure at said one side of the piston,Aand means engaging the outer faces of the outer plates of said stackand responsive to said working pressure within said cylinder at said oneside of said piston to apply a compressive force to said stack of platesnormal to the faces thereof.

References Cited in the le of this patent UNITED STATES PATENTS

